Add media-library sub-team and update related configurations (#133)

- Added "media-library" sub-team under leadgen in highlevel-teams.json.
- Updated LEADGEN_SUB_TEAM in process-issue.js to include MEDIA_LIBRARY.
- Updated PRODUCT_CHANNELS in process-issue.js to map "media-library" to Ajay Dev.
- Included "media-library" in various issue templates for bug reports and feature requests.